The traditional Hall-Heroult method has still been employed in aluminum electrolysis industry so far, cryolite-alumina has served as the basic system for electrolyte all the time, and the existing electrolytic cell with pre-baked anode mainly adopts carbon cathode. Carbon cathode is not wet for aluminum liquid and is under the corrosion of cryolite for a long time, so in order to prolong the service life of electrolytic cell, an inert coating typically needs to be coated on the surface of carbon cathode. Due to excellent wettability for aluminum liquid and superior corrosion resistance to cryolite, transition metal borides are quite suitable for the use as carbon cathode surface coating. Meanwhile, transition metal borides can be used for preparing inert anode material owing to their excellent wettability for aluminum liquid, superior corrosion resistance to cryolite and good conductivity and thermal impact resistance. Transition metal borides like titanium boride are quite high in price, so it is difficult to implement their wide use in preparing carbon cathode surface coating material and inert anode material at present.
The current transition metal borides is mainly derived from direct reaction between titanium, zirconium, chromium or vanadium and monomer boron at high temperature. Since the yield of monomer boron in industrial production is not high (typically below 90%) and the production cost is high, expensive monomer boron results in expensive transition metal boride, further limiting large-scale industrial production of transition metal boride.